1. Field of the Invention
The present invention relates to transfer systems, and particularly to a transfer system for applying transfer control to bundling which bundles a plurality of paths into one path.
2. Description of the Related Art
The amount of information handled in information communication networks has been exceedingly increased, and further advanced multimedia service is expected at a wider bandwidth. In such a situation, dense wavelength division multiplex (DWDM) has been developed as a high-traffic transfer technology.
DWDM multiplexes light beams having different wavelengths at a high density to transfer a plurality of signals by one optical fiber at the same time. For example, with the use of DWDM, several tens to several hundreds of wavelengths (wavelength paths) each having a transfer capacity of 10 Gbps can be multiplexed in one optical fiber.
In this case, it is possible that 192 time division multiplexing (TDM) paths each having a transfer capacity of 51.840 Mbps are multiplexed in one wavelength path, and several hundreds of multi-protocol label switching (MPLS) paths are multiplexed in one TDM path at synchronous transport signal (STS)-1.
FIG. 48 shows the concept of a multiplexed path structure. A plurality of wavelength paths are multiplexed in one optical fiber. In each wavelength path, 192 TDM paths each having a transfer capacity of 51.840 Mbps are multiplexed. In each TDM path, several hundreds of MPLS paths are multiplexed.
The figure also shows hierarchical multiplexing at layers. Cross-connect control is applied only to the MPLS paths at nodes A and G. Cross-connect control which includes interconversion between MPLS paths and TDM paths is performed at nodes B and F. Cross-connect control which includes interconversion between TDM paths and wavelength paths is performed at nodes C and E. Cross-connect control is applied only to the wavelength paths at a node D.
The system scales of information communication networks have been greatly extended together with an increase in subscriber-data traffic caused by the use of the Internet and other factors. Therefore, to perform efficient signaling and routing in networks, a technology called a generalized MPLS (GMPLS) has attracted attention these days, and has been standardized by Internet Engineering Task Force (IETF).
GMPLS applies signaling and routing to signals on optical networks. An optical signal is switched by identifying its wavelength and a routing path is determined for an optical signal without converting the optical signal to an electric signal in GMPLS whereas a label is attached to a packet and a routing path is specified in MPLS.
In network management, provision (including data inputs and operation settings) is conventionally performed for each node with the use of a transaction language-1 (TL-1) command (language specifications determined by the north-America GR standard) and others. In GMPLS signaling, however, provision can be specified in units of paths.
In GMPLS, the efficiency of maintenance and management in such network management is increased by applying an extended control protocol for a subscriber-data IP network to a carrier-side network to integrate path setting and maintenance with those of the IP network.
In MPLS, signaling and routing are implemented only at a packet layer. In GMPLS, signaling and routing are controlled at all layers, an optical-fiber layer, a wavelength layer, a TDM layer, and an IP layer. Therefore, route information should be advertised for all the layers.
To specify a wavelength path by signaling, each node should have route information which specifies physical connections between nodes by optical fibers. Therefore, all nodes need to advertise the route information of local-node physical links to the network. When such physical route information is advertised, physical paths are configured between nodes, and a wavelength path can be specified between nodes.
Further, to specify a TDM path by signaling, each node should have route information which specifies wavelength paths between nodes. Therefore, all nodes need to advertise the wavelength paths as logical links to the network. It is also necessary to have TDM-path route information when an MPLS path is specified.
When 20 optical fibers are connected to one node, for example, route information which specifies the connected destination nodes of the 20 physical links should be advertised. Also for adjacent nodes thereof, physical-link route information should be advertised. This is because only links which advertise routing protocol are recognized.
When each of the 20 optical fibers has 0.100 wavelength paths, for example, route information should be advertised for 2,000 logical links (=20 optical fibers×100 wavelength paths).
When one wavelength path has 100 TDM paths, for example, route information should be advertised for 200,000 logical links (2,000 wavelength paths×100 TDM paths). Route information to be advertised is increased as more layers are used, sharply increasing the load of the network.
To solve such a problem, IETF has been examining link bundling (IETF draft: draft-ietf-mpls-bundle-01.txt). In link bundling, control is made such that paths having the same destination are bundled into one path (bundled link) and advertised. Even when a transmission-side node and a receiving-side node have different paths at the middle, the paths can be bundled into one link in link bundling.
FIG. 49 shows the concept of link bundling. In the figure, a plurality of wavelength paths are bundled into one path (bundled link), and a plurality of TDM paths are bundled into one bundled link. Connection nodes are advertised that the paths are bundled into one bundled link.
Since there are several hundreds to several hundred thousands links in total in the optical-fiber, wavelength, TDM, and IP layers in GMPLS, control cannot be made if each route information is advertised as in a conventional router. An object of link bundling is to advertise paths having the same destination as one path to reduce the amount of information handled by routing protocol and to improve scalability.
There has been conventionally proposed a system for implementing communications independent of the signal transmission rate and the format by assigning service to each wavelength path in which a communication channel between points is allocated to the wavelength, as an optical-network technology which includes a bundling function. The system is disclosed, for example, in paragraphs [0020] to [0039] and FIG. 1 in Japanese Unexamined Patent Publication No. Hei-11-98077.
In the conventional link-bundling technology proposed by IETF, described above, the information of each component link which forms a bundled link should have been already advertised because a bundle is specified for links which have already existed. Therefore, until a bundled link is specified, each node needs to control route information related to all component links. In addition, after a bundled link is specified, the route information of component links needs to be deleted. This imposes a load on each node, which means that the original object of link bundling has not been sufficiently achieved.
Further, conventionally, a bundle is manually specified and managed for links which have already existed, and the same bundle setting is required for the transmission-side node and the receiving-side node. Therefore, a human mistake may occur at setting operations, and maintenance needs a long time, generating a low efficiency in maintenance and management.
Furthermore, IETF does not explicitly determine whether a bundled link needs to be once released when a component link is added or deleted after the bundled link has been specified.